Flintlock, my reaction is that 12,000 on 12x6 w/10% nitro is a bit on the fast side. For your first break-in run, I would start with sloppy rich needle setting, and then once you have it started, turn the needle in just past the point where it goes from four-cycle to two-cycle. This would be a definitely rich setting, and you should be seeing plenty of exhaust. I would not be looking for 12,000 rpm until you are maybe into your fifth tank. Tach your engine at WOT but needle just over the two-cycle break, and let it run five minutes at that setting. Then shut down, let it cool to the point where you can touch your finger to the head without getting burnt (figure at least a 10-minute cool-down). Then on subsequent runs turn your needle in for a few hundred rpm and go another five minutes. After the engine is running at a stable speed, give the fuel line a (brief) hard pinch and listen for a higher note. If you don't get it, or the engine stops, open the needle a few clicks, because you are at peak. If you do get it, leave the needle alone until you finish another 5-minute run/10-minute cool-down. I broke in a Tower .75 a month ago, and got it turning a 12x8 apc prop at 11,100 static on 15% nitro, pulling an old 60-size Easysport I re-built. I got a lot of comments on the vertical acceleration out of my low and slow passes. It pulls straight up indefinitely.